Friction elements and method of making same



factory drying of the binder oil, and so Patented June 2 4, 1930 UNITED STATES PATENT OFFICE IZADOR J. NOVAK, OF BBIDGEPOE'T, CONNECTICUT, ASSIGNOR, BE MESNE ASSIGN- MEN'IS, TO RAYBESTOS-MANHATTAN, INC., A CQRPORATION OF NEW JERSEY FRICTION ELEMENTS AND METHOD OF MAKING SAME No Drawing. Original application filed January 28, 1924, Serial No. 688,108. Divided and this application filed larch 11, 1928. serial No. 346,271.

This application is a division of an earlier hardening temperature. This would be exapplication filed by me under'date of J anuary 23, 1924, Serial No. 688,108.

The present invention relates to friction,

elements and process of making same, said friction materials comprising clutch facings, friction blocks, and the like, formed from a base of asbestos pulp or woven asbestos tape saturated with an or anic dr 'ngoil binder, without the aid 0 any so vent or carrier for the binder.

The method generally employed at the present time in the manufacture of clutch facings and other friction elements when using an asbestos pulp base saturated with an organic drying oil binder is essentially as follows:

Asbestos sheeting in the desired thickness 7 and form is impregnated at room temperature with a solution of the liquid binder, for instance, linseed oil, in a suitable solvent, such as gasoline or the like. After impregnation, the solvent is removed by heating the impregnated asbestos in an oven which heating is continued, to dry and harden the oil. It has been found by those skilled in the art, that in employing a solvent, the proportion of binder oil to solvent may not safely be raised above 3 to 1 without encountering a glazing of the surface due to exudation of binder oil from the interior portions of the impregnated pulp to the outside with resultant hardening there,

which thereupon effectually seals the interior from the access of air needed for satisprolongs to a disproportionate time the heating period essential for the complete hardenin of all the binder.

Thus, or example, it was found that a clutch facing which normally cured in .clutch facing such a'described above so as to prevent the formation of a glaze by means of a long drying at alow temperature 'previous to exposure to thenormal tremely objectionable in practice due to the care necessary in regulation of temperatures, and the prolonged time of cure. It will be seen, therefore, that not only is the loss of a considerable amount of solvent necpletely filled, as in the process to be described below.

Another disadvantage attachable to this method of saturation and cure lies in the fact that it is practically impossible to cure a dryin oil in an asbestos pulp base uniformly ard from center to outside even when there is no decided glazing in a reasonable. length of time such as 24 to 60 hours, in any thickness greater than inch, due to the gradual sealing of the surface pores in a cure which must commence from the outside and proceed inwards. By the method described below the whole thickness is evenly cured to begin with, and there is no sealing of the interior portions. I have cured asbestos pulp or wood fibre pulp in thicknesses as high as one inch, and believe the method capable of use in curing still greater thicknesses. I

My invention comprises essentially the impregnation of the asbestos base such as asbestos pulp, or woven yarn with an organic drying oil, the partial hardening of the oil by heat treatment under pressure with partial or complete exclusion of air, or in a non-oxidizin atmosphere, with or without pressure an the final hardening of the oil by heat treatment in an oxidizing atmosphere, with or without pressure. The last operation may, of course, be omitted if partial hardening of the oil is suflicient for the {111F050 desired.

T e ollowin description exemplifies one illustration of t procedure, which I have practiced in the fabrication of friction elements for use in automobile clutches: Annular ring blanks of approximately the desired dimensions. are stamped out from asbestos mill board by the use of a' die and die ress. These rings are then dried free of moisture and immersed for ten minutes in a bath of China-wood oil, heated to 300 F. This is equivalent to a complete saturation at this temperature. The rings are then removed from the bath and allowed to stand at room temperature until the. surface feels fairly dry to the touch. This may take from 12 to 24 hours. The purpose of this operation is merely to lessen the tendency to adhere during the immediately subsequent cure, and is not essential to the process. A coating of fine graphite may then be applied to the rings and they are stacked in any desired number, the pack being held to ether between two iron plates connected Ty a bolt. The entire pack may then be subjected to a temperature of 400 F. for say, four hours. On removal from the oven, the pack is allowed to cool and the rings are then separated. At this point the oil has been par- 14 Brinnell.

twenty hours, depending on the thickness of tially hardened, and the rings are firm, and fairly strong, but not yet sufiiciently hard for satisfactory use in a clutch. They may be then hung on spindles and baked in the open in an oven heated to 325 F. for a pe riod sufficient to bring the hardness up to This may take from six to the rings. After the final cure is complete, the rings may be sanded down to size and the graphite removed from the surface in the same operation. The edges may be brushed, or if necessary, turned down to size in a lathe. vThe finished ring is a roduct superior to any made with the aid 0 a solvent as carrier for the drying oil, in density, toughness, flexibility, resistance to shock, and general machine ability.

- a large number of applications of this procfacture.

. means for the hardening ess to the art of friction element manu- I have used it for friction blocks up to one inch in thickness. The method for producing brake linings with an asbestos pulp base and drying oil binder is a simple operation, the resultant product being very durable. Cone clutch facings have substantially the same characteristics as the brake lining. Insulation sheeting made with a use of a solvent as vehicle for carrying the- The invention may be "applied to thick The foregoing illustration is only one of woven fabrics withe ually good results, and brake lining, clutch acings and other'products with woven fibrous base show the same advantageous characteristics that are evidenced in pulp base materials.

The drying oil used in my invention may include any oil which will harden under the conditions described above. The true drying oils such as linseed, China-wood, erilla, etc., are the best for the ends desire but I have found that many so called non-drying 'or semi-drying oils such as palm, corn, ra eseed, etc., also give very satisfactory resu ts by the use of the method specified.

Oils or combinations of oils which do not have a marked tendency to glaze, especially China-wood and mixtures of it, with other oils, when used as a saturant as heretofore described, may be partially hardened, if desired, in a substantially non-oxidizing atmosphere such as carbon dioxide, nitrogen, flue gas, ammonia, etc., at an elevated temperature, say from 300 to 500 F. w1th or without pressure, depending on the character of theoil. Oils with marked tendency to glaze, such as linseed when used as a sat- "urant, as heretofore described, may be partially hardened in an inert gas under pneumatic pressure, while China-wood oil which has only slight glazing tendency; may be hardened with the gas at atmosp er1c pressure.

I claim as my invention:

1. The method of produclng friction elements, which comprises impregnating asbestos fibrous elements with a drylng Oll, stacking the impregnated elements 1n the form of a close pack, partially hardemng the oil by heat treatment of the impregnated elements while maintained in said close pack, separating the elements and finally hardening the oil by heat treatment of the partially cured elements while maintaining them in spaced or separated relation apart from each other in an oxidizing atmosphere.

2. The method of producing friction elements which comprises impregnating asbestos fibrous elements with a drying oil, stackin the impregnated elements 'inthe form 0 a close pack, and partially hardening the oil by heat treatment of the impregnated elements while maintained. in said close pack to produce a non-glazed uniformly hardened product.

3. The method of producing friction elements which comprises impregnating asbestos fibrous elements with a dryin oil at an elevated temperature, stacking t ejifimpre nated elements in the form of a close pac partially hardening the oil by heat treatment of the impregnated elements while maintained in said close pack, se arating the elements and "subsequently ally hardenin'gl'the oil by heat treatment of the partially, cured elements while maintaining them in separate relation from each other in an oxidizing atmosphere.

4. The method of producing friction elements which comprises impregnating asbestos fibrous elements with a drying oil at an elevated temperature, stacking the impregnated elements in the form of a close pac and partiall hardening the oil by heat treatment of t e impregnated elements while maintained in said close pack to produce a non-glazed uniformly hardened product.

' 5. The method of producing friction elements which comprises impregnating asbestos fibrous elements With a saturant comprislng a drylng oil, stacking the lmpre nated elements in the form of a close pac partially hardening the saturant by heat I treatment of the impregnated elements while maintained in' said close pack, then sep 'ating the elements and subsequently final y hardening the saturant by heat treatment of the artially cured elements while soseparated rom each other in an oxidizing atmos here.

6. he method of producing friction elements which comprlses impregnating asbestos fibrous elements with a saturant stacking the impregnated elements in the form of :1 close pack, and partially hardening the saturant by heat treatment of the impregnated elements while maintained in said close pack to produce a non-glazed uniformly hardened product. a In testimony whereof I aflix my signature.

IZADOR J. NOVAK. 

